This invention relates to magnetic tape recorders and preformatted tapes adapted for use therein, and in particular, to such recorders adapted for data recording purposes utilizing magnetic recording tapes preloaded in data cartridges. Data recording cartridges and recorders adapted for their use are notably disclosed and claimed in U.S. Pat. No. 3,692,225 (Von Behren). In the cartridge there disclosed a magnetic recording tape is preloaded in a reel-to-reel type enclosure together with an endless flexible belt in frictional contact with the tape on both reel hubs for incrementally bidirectionally driving the tape, including rapid accelerations and decelerations, such as are encountered in digital data recording and playback. The system there set forth represents many advantages such that data cartridges are filling an important need in the computer industry, especially as backup storage for mini-computer and microprocessor based systems. Such tapes are typically written and read using a redetermined format. The format is based on a physical and logical block structure. The tape is usually divided up into tracks and each track contains a number of physical blocks. These blocks are of a predetermined size and contain various types of information related to the structure and content of the block as well as the data that comprises the block. The track and physical block structure is further organized as logical blocks which are conceptualized in a hierarchical fashion. Each logical block is composed of a number of physical blocks. The number of physical blocks in a logical block varies depending on the application of the tape drive. In a preferred embodiment particularly pertinent to the present invention there are a number of tracks on each tape and each track has a variable number of physical blocks and further the logical block cannot span more than one track. Those skilled in the art will appreciate that the methods of the current invention are equally applicable to situations where logical blocks span multiple tracks as well as in the situation where logical blocks span a number of tapes.
Referring now to FIG. 1 which shows such a recording tape 10 written in a serpentine fashion. The tape 10 is of arbitrary length and contains a plurality of tracks. Tape 10 is shown as having seven tracks in this embodiment of the invention. The writing of information on the tape occurs in a serpentine fashion whereby the tape is read and written by a single read, write head combination which reads the tape in a forward direction indicated by arrow 12 and in a backwards direction indicated by arrow 14. The serpentine tape 10 of FIG. 1 has seven tracks written from the center track 0 to the outer-most track 6. Track 0 is written in the forward direction, track 1 is written in reverse direction, track 2 is written in the forward direction, track 3 is written in the reverse direction, track 4 is written in the forward direction, track 5 is written in the reverse direction and finally track 6 is written in the forward direction. Those skilled in the art will appreciate that the serpentine format may contain a predetermined number of tracks which is determined by the physical characteristics and dimensions of the tape and the tape reading/writing mechanism. Those skilled in the art will appreciate that the serpentine format is advantageously employed to void the necessity of formatting the tape.
The serpentine format avoids the necessity of formatting the tape by providing a tape header on certain tracks. In this referred embodiment of the invention the tape header appears on even tracks. Those skilled in the art will appreciate that the tape header could occur on all tracks. The elimination of the need to format a tape prior to the reading or writing of data saves the time required to run the tape from the beginning of the first track to the end of the last track.